1. Field of the Invention
This invention relates to a distance measuring apparatus of the target tracking type, and more particularly to a distance measuring apparatus which measures the distance to a moving object such as an automobile while tracking the moving object. The invention further relates to a rear-end collision preventing apparatus incorporating the distance measuring apparatus and an alarm for preventing a rear-end collision between objects such as an automobile following another automobile.
2. Description of Related Art
Various methods of identifying an object in front of a moving vehicle have been proposed. For example, Japanese Patent Laid-Open Application No. Heisei 2-241855 discloses an image identifying method based on an optical flow system. Japanese Patent Laid-Open Application No. Heisei 3-170012 discloses a data matching method based on window processing.
The conventional methods, however, require successively comparing picture elements and consequently require processing of a very large amount of data of about 1 to 10 megabytes. Accordingly, an identifying apparatus which incorporates the conventional methods have not been put into practical use in vehicles which require a high rate of image processing.